The technical field generally relates to control systems for hybrid power trains. Hybrid power trains utilize more than one power source to generate the torque and power needed to meet the current demands for the application in which the hybrid power train is installed. The installed hybrid power train includes the first power source (e.g. an internal combustion engine), the second power source (e.g. an electric motor/generator and associated battery pack), and the application in which the hybrid power train is positioned and interfaced. The entire system may further include interfacing hardware, electronic controllers, linking networks and electrical components, an engine compartment, a vehicle body, a transmission, etc.
Various portions of the entire system may be provided by different manufacturers, and/or may be manufactured at varying locations or manufacturing times. The control of various portions of the hybrid power train may be distributed between manufacturers, and/or distributed between various computing devices and hardware across the system. The control of various portions of the hybrid power train may further be integrated with devices outside of the system that includes the power sources and the electronics integrating the power sources.
Non-limiting distribution examples include controls for the internal combustion engine provided with the engine by a first manufacturing entity, controls for an electric portion of the hybrid power train provided by a second manufacturing entity, and installation of the power sources into a vehicle provided by a third manufacturing entity. Another distribution example includes a first manufacturer providing engine controls and interfacing to the application, with a second manufacturer providing controls for the electric portion of the hybrid power train. Any distribution of the controls and hardware can present control interface challenges in certain circumstances.
A hybrid power train system requires, generally, a determination of the total torque and/or power requirement for the powered application, a determination of the contributions of the available power sources that will be provided to meet the total torque and/or power requirement, and finally control of the individual power sources to meet the determined individual contributions. Applications where a number of manufacturing entities provide different portions of the entire system, interfaces are created within the control system for the hybrid power train system. For example, the determination of the total torque and/or power requirement is generally provided by a device outside of the hybrid power train system and communicated to the hybrid power train system—for example from an accelerator pedal, a cruise control switch, a PTO switch, or a similar device.
When a first control element that determines the total torque and/or power requirement is on a separate electronic device from a second control element that determines the contributions of the available power sources, the total torque and/or power requirement must be communicated to the second electronic device over a datalink or other network device. The second control element may be on a separate electronic device from a third control element that provides specific engine control to meet the engine contribution portion of the total torque and/or power requirement, and/or on a separate electronic device from a fourth control element that provides specific motor/generator control to meet the electric side contribution of the total torque and/or power requirement. Additionally, a fifth control element may be present to determine energy flux requirements within the electric side, including charging or discharging of the battery pack, the available current and power capacities of the motor or generator, etc. The fifth control element may likewise be on a separate electronic device from one or more of the other control elements, requiring further datalink communications.
Each situation where control elements are provided on separate computing devices, a potential lag period is introduced within the control loop. For example, the first control element determines a total torque requirement which passes to the second control element over a datalink with a lag, in a nominal case, of up to about 20 ms. The second control element determines the torque partitioning, and passes the internal combustion engine portion of the torque requirement introducing another lag of about 20 ms. Additionally, the initial torque requirement may have been communicated to the first control element via a datalink (e.g. with an accelerator pedal position published on a datalink rather than hard-wired into the controller), providing additional lag between the torque request and final response.
Further, because control elements may be executing at different execution rates, the age of the information between control elements may be somewhat variable. For example, where the first control element publishes the total torque requirement to the datalink each 15 msec, and the second control element reads the total torque requirement from the datalink each 10 msec, the second control element will receive information having a delay with a beat pattern where some data is relatively new and other data is relatively stale.
Accordingly, each datalink interface introduced into the entire system control loop (i.e. from the application overall torque request until the final commands to all hardware elements) degrades the performance and responsiveness of the system. The degradation can be managed by methods known in the art, for example by introducing synchronous datalink communications such that control elements provide information according to a schedule and/or with time information included within the communications. However, synchronous communications are more complex and require additional costs in the system design and hardware requirements. Additionally, the use of synchronous communications also requires agreement among the designers of the various control elements. The degradation can also be avoided by removing datalink communications from the system and including all control elements within the same hardware computing device. However, the inability to provide distributed control elements requires that all manufacturing entities have access to the controller, which may introduce conflicts in control and ownership of the content of the final controller. The inability to provide distributed control elements across hardware devices may also introduce complications in manufacturing and limitations in final application design. Further, it may be difficult or impractical to coordinate all manufacturing entities to create software control elements that are compatible, that meet requirements for memory consumption in storage and in real-time operation, that use the correct data types, that are delivered on time and in the correct versions, etc.
Datalink communication lags may also be managed by providing dedicated hardware communications. For example, a first hardware device may provide an output voltage that is wired directly to a second hardware device accepting in input voltage. The communicated parameter is provided by an agreed upon schedule of the output voltage to the communicated parameter value. A sensor connected to the hardware device is a common example of such a hardwired communication. However, hardwired communications are generally undesirable because they introduce costs due to manufacturing, the implementation of standards for connectors and wires, risks to the reliability of the system, and competition for the generally limited number of input and output pins (or other I/O hardware) available on hardware computing devices.
It is also desirable that a hybrid power train, or portions of a hybrid power train, be capable of being installed in a range of applications, where the range of applications include a range of control capabilities. For example, a manufacturer may develop a highly capable second control element to determine the power distribution between the engine and the electric side, but rely upon a base hybrid power train controller to control other aspects of the system. Additionally, it is desirable that a hybrid power train be capable of being flexible over time without the entire control system requiring replacement when a different control burden is placed on the hybrid power train. For example, a manufacturer of an application may develop an intelligent transmission that determines the total torque and/or power requirement for the application, and it is desirable that the application can be upgraded with the intelligent transmission without requiring a complete change of the hybrid power train control. Further, the manufacturer may wish to intermittently provide control input, for example determining the battery state-of-charge requirement when transient city driving is detected, but at other times allow a base control scheme to control the application.
Therefore, further technological developments are desirable in this area.